The present invention relates to a new and improved construction of a net- or chain-like vehicle traction device for rubber tired vehicular wheels -- also sometimes referred to in the art as an anti-skid device --, which is of the type comprising a traction unit or traction means, for instance in the form or wire netting or chains for increasing traction between the outer peripheral surface of the wheel and the ground upon rotation of the wheel about its axis and a tightening mechanism effective at least at one side of the wheel in the circumferential or peripheral direction when the vehicle traction device is mounted at the wheel.
Net-like vehicle traction devices, such as snow chains, composed of net-like coverings formed of rubber encased wires or the like, oftentimes possess tightening or tensioning means effective at least at one side of the wheel in the circumferential direction for facilitating the mounting of the vehicle traction device. The tightening or tensioning means can embody spring elements which, during mounting of the vehicle traction device, are elongated or extended and exert a traction or tensioning force in the mounted condition.
Such construction of vehicle traction device facilitates the mounting thereof in contrast to those state-of-the-art constructions where it is necessary to manually tighten a non-expansible chain and to positively suspend a hook into one of the chain links intended to receive the same, in order to obtain a relatively tight contact of the vehicle traction device against the vehicular wheel or tire. Such flexible tightening means are particularly advantageous from the standpoint of facilitating the mounting of the vehicle traction device when they serve for producing a circumferential force at the inboard side of the wheel, where it is difficult and cumbersome work to hang-in hooks or the like.
However, elastic tightening means are associated with the drawback that they fail to provide a faultless fixation of the vehicle traction device in the presence of forces which arise when such vehicle traction device is moving along the road. It is for this reason that tightening or tensioning devices employing spring elements, for instance used for vehicle traction devices for automobile tires, have not found wide spread acceptance in practice. Attempts have been made to improve fixation of the traction device by increasing the spring tension, yet when this is done it is necessary to exert so much force manually during mounting of the traction device that it is virtually impossible to mount the same outside of a garage or other service station or without resorting to the aid of additional tools or other mounting expedients.